1. Field of the Invention
The present invention elates to a power semiconductor device, and more particularly, to a power semiconductor device including a radiating surface cooled by a cooling unit.
2. Description of the Background Art
Japanese Patent Application Laid-Open No, 2012-191010 discloses a semiconductor device on which power semiconductor elements are mounted. The semiconductor device is attached to a cooling fin to which thermal conductivity paste is applied to dissipate heat generated by the semiconductor elements and is fixed with bolts to be used.
In the semiconductor device, a temperature of a radiating surface to which the cooling fin is attached with the thermal conductivity paste therebetween may greatly vary with an operating state of the power semiconductor elements. This changes a warped shape of the radiating surface, and a phenomenon in which the thermal conductivity paste is extruded from the portion between a cooling surface and the cooling fin may occur. This phenomenon is also referred to as a grease pump-out. A repetition of the pump-out under a heat cycle increases a heat resistance between the radiating surface and the cooling fin, and thus heat dissipation characteristics of the power semiconductor device greatly deteriorate.